Dana Reeve, widow of Superman actor and health activist Christopher Reeve, has died of lung cancer at age 44.

The head of the Christopher Reeve Foundation announced Tuesday that Reeve died on Monday. She announced in August that she had lung cancer.

Christopher Reeve died of heart failure in 2004, nine years after the horse-riding accident that left him paralyzed from the neck down. After his death, Dana Reeve became the driving force of the foundation they co-founded to help find better treatment for paralysis victims.

The couple is survived by their teenage son. Christopher Reeve also had two children from an earlier marriage.

Some information for this report was provided by AP.